Roman Numeral Converter
Convert any whole number from 1 to 3999 to Roman numerals, or convert Roman numerals back to decimal. Shows step-by-step breakdown and symbol reference.
Quick Reference
I
1
IV
4
V
5
IX
9
X
10
XL
40
L
50
XC
90
C
100
CD
400
D
500
CM
900
M
1000
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How It Works
Roman numerals use 7 symbols: I(1), V(5), X(10), L(50), C(100), D(500), M(1000). All other numbers are combinations of these.
I V X L C D M2024 = MMXXIVSymbols add when a larger or equal value precedes a smaller one: VIII = 5+1+1+1 = 8. Write from largest to smallest.
Larger before smaller = addVIII = V+I+I+I = 8A smaller symbol before a larger means subtraction. Only 6 pairs: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.
6 valid subtractive pairs onlyIV=4, XL=40, CM=900I, X, C, M can repeat up to 3 times. V, L, D never repeat. IIII is invalid (use IV). MMMM is invalid (3999 is max).
Max 3 repetitions for I,X,C,MIII=3 valid; IIII=4 invalid (use IV)Starting with M(1000): subtract the largest symbol that fits, write it, repeat. Continue down through CM,D,CD,C,XC,L,XL,X,IX,V,IV,I.
Greedy subtraction from largest symbol2024: M(1024 left), M(24 left), X(14), X(4), IV → MMXXIVRoman numerals originated in ancient Rome (~800 BCE). The subtractive notation was standardized in the Middle Ages. Still used today for formal contexts.
Seven symbols, additive/subtractive rulesSuper Bowl LVIII, Henry VIII, Copyright MMXXIVQuick Reference
Common examples — verify instantly above.
To Roman
2024
MMXXIV
To Roman
1999
MCMXCIX
To Roman
4
IV
To Roman
9
IX
From Roman
XIV
14
From Roman
XLII
42
From Roman
MMXXIV
2024
From Roman
MCMXCIX
1999
Tips & Shortcuts
The six subtractive pairs to memorize: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900. All others are additive.
I, X, C, M can repeat up to 3 times. V, L, D never repeat. 8=VIII (not IIX — subtractive only applies to the 6 pairs).
To convert quickly: handle thousands first (M), then hundreds (CM/D/CD/C), then tens (XC/L/XL/X), then ones (IX/V/IV/I).
A quick check: if you see VV, LL, or DD, the numeral is incorrect — these symbols never repeat.
MMXXIV = 2024: MM=2000, XX=20, IV=4. Break it into thousands, hundreds, tens, ones.
The "bar notation" for large numbers (M with a bar = 1,000,000) is not standard in this calculator, which supports 1-3999.
Common Mistakes
Writing IIII instead of IV for 4
Subtractive notation: 4 = IV, 9 = IX. Do not write IIII or VIIII.
Using invalid subtractive pairs like VX or LC
Only 6 valid pairs: IV, IX, XL, XC, CD, CM. VX, LD, DM etc. are not valid Roman numerals.
Repeating V, L, or D
V, L, D cannot repeat. 10 = X, not VV. 100 = C, not LL. 1000 = M, not DD.
Repeating I, X, C, M more than 3 times
Maximum 3 repetitions. 40 = XL, not XXXX. 4 = IV, not IIII.
Reading Roman numerals right to left
Read left to right. A smaller value before a larger means subtract; otherwise add.
Assuming all clock IIII is an error
Many clocks traditionally use IIII instead of IV — this is a historical stylistic choice, not an error.
Frequently Asked Questions
I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Subtractive pairs: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.
Subtractive notation: I before V means 5−1=4. This is more compact and was standardized. However, clock faces often use IIII.
3999 = MMMCMXCIX. Without special notation, Roman numerals max at 3999. Historically, a bar over a numeral multiplied it by 1000.
No. Roman numerals have no symbol for zero. The concept of zero came to Europe through Arabic numerals.
They are used for copyright years, Super Bowl numbers, monarchs (Henry VIII), movie sequels, and chapter headings where tradition and formality matter.
MM=2000, XX=20, IV=4 → 2000+20+4 = 2024.
3,999 (MMMCMXCIX) is the largest in standard notation — MMMM would require four consecutive M's which is non-standard. Some systems add a bar over letters to multiply by 1,000 (V̄ = 5,000, X̄ = 10,000), reaching up to 3,999,999. Modern uses rarely exceed a few thousand: MMXXV = 2025, Super Bowl LIX = 59, copyright notices, chapter numbering, and clock faces.
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